An important consideration in performing surgery is the “hand” or “feel” of the suture being used to close wounds. These are reflected by the knot “tie-down” and “run-down” characteristics of the suture. Tie-down characteristics refer to the ease with which a surgeon can tie a knot, and the ability of the suture to remain knotted without unraveling. Run-down characteristics refer to the ability of a surgeon to make one or more “throws” of a knot in the suture and have it run down a suture to the knot site. Generally, these characteristics relate to the lubricity and stiffness of the suture; lubricity facilitates the tying of a knot whereas stiffness makes tying a tight knot more difficult and increases the probability of kinking of the suture and/or unraveling of the knot.
Multifilament sutures, such as braided or twisted sutures, have better softness and flexibility than monofilament sutures and can be more easily knotted. However, multifilament sutures can have a rougher surface or more “grabbiness” than monofilament sutures and significant dead space (interstices) between filaments. The dead space can be reduced by impregnating the suture with a filler material. Filler material can help lubricate the suture fibers and enhance flexibility.
Many sutures materials are bio-absorbable and susceptible to hydrolysis. For these sutures, extreme care must be taken to rigorously exclude moisture during storage. For example, the strength of polyglycolic acid sutures undergoes significant deterioration during long term storage in the presence of even small amounts of water. Prior to packaging, these sutures are heated for an extended period to remove essentially all the water. They are then promptly packaged in a moisture free environment.
Due to various drawbacks in this approach, other approaches to improving the storage stability of absorbable sutures have been proposed. For example, it has been proposed to use filler material to improve the storage stability of multifilament sutures. In one example, the filler material contains at least one water-soluble liquid polyhydroxy compound and/or ester thereof. It has also been suggested that the polyhydroxy compounds can improve the hand of the suture and are capable of dissolving a variety of useful drugs and can be used as vehicles to deliver drugs to a wound site.
At present, many biocompatible polymers are known. For example, poly(ethylene glycol) (PEG) is a water-soluble polymer showing excellent biocompatibility and has been frequently used in biomedical applications. Similarly, polysiloxanes are widely used in the biomedical field and have been the subject of intense study both in the academic field as well as in industry.
Amphiphilic polymer networks have also been identified as potentially useful biomaterials. Amphiphilic polymer networks are co-continuous assemblages of hydrophilic and hydrophobic polymer chains that are able to swell in both hydrophilic solvents (e.g., water) and hydrophobic solvents (e.g., a liquid hydrocarbon). Because these materials swell in water, they generally fall into a class of compounds known as “hydrogels”.
The first amphiphilic membranes for biomaterials were developed over a decade ago. These were networks of hydrophilic polymers with the hydrophobic crosslinking agent, di-methacryl-telechelic polyisobutylene (MA-PIB-MA). Synthesis was accomplished by living carbocationic polymerization, which involves free radical copolymerization and can use a variety of inexpensive, commercially available monomers, for example, N-dimethylaminoethyl methacrylate and dimethyl acrylamide.
Kennedy, U.S. Pat. No. 4,486,572 discloses the synthesis of styryl-telechelic polyisobutylene and amphiphilic networks comprising the copolymerization product of the styryl-telechelic polyisobutylene with vinyl acetate or N-vinyl-2-pyrollidone. Kennedy, U.S. Pat. No. 4,942,204 discloses an amphiphilic copolymer network swellable in both water and n-heptane but insoluble in either, comprising the reaction product of an acrylate or methacrylate of a dialkylaminoalkyl with a hydrophobic bifunctional acryloyl or methacryloyl capped polyolefin. The preferred embodiment disclosed is an amphiphilic network having been synthesized by the free-radical copolymerization of a linear hydrophobic acrylate (A-PIB-A) or methacrylate capped polyisobutylene (MA-PIB-MA) with 2-(dimethylamino)ethyl methacrylate (DMAEMA). In a continuation-in-part to U.S. Pat. No. 4,942,204, Ivan et al. U.S. Pat. No. 5,073,381 discloses various amphiphilic copolymer networks that are swellable in water and n-heptane that comprise the reaction product of a hydrophobic linear acryloyl- or methacryloyl-capped polyolefin and a hydrophilic polyacrylate or polymethacrylate, such as N,N-dimethylacrylamide (DMAAm) and 2-hydroxyethylmethyl methacrylate (HEMA).
Hirt, U.S. Pat. No. 5,807,944 discloses a copolymer of controlled morphology comprising at least one oxygen permeable polymer segment and at least one ion permeable polymer segment, wherein the oxygen permeable segments and the ion permeable segments are linked together through a non-hydrolysable bond. The oxygen-permeable polymer segments are selected from polysiloxanes, perfluoroalkyl ethers, polysulfones, and other unsaturated polymers. The ion permeable polymers are selected from cyclic imino ethers, vinyl ethers, cyclic ethers, including epoxides, cyclic unsaturated ethers, N-substituted aziridines, beta-lactones, beta-lactanes, ketene acetates, vinyl acetates and phosphoranes.
U.S. application Ser. No. 09/433,660 discloses an amphiphilic network comprising the reaction product of hydrophobic crosslinking agents and hydrophilic monomers wherein the hydrophobic crosslinking agents are telechelic three-arm polyisobutylenes having acrylate or methacrylate end caps and wherein the hydrophilic monomers are acrylate or methacrylate derivatives.
Sutures and surgical staples can be used for anastamoses. Anatomoses involves the joining of veins or arteries. During anastamoses, damage to the neointimal layers of the veins and arteries (the interior layers) occurs through physical manipulation and the device used for joining. This damage affects the healing process and can result in the failure of an arterial or veinous graft. There remains a long felt need for more successful anastamoses procedures.